RESUMO
Recent technological advances allowing direct in vivo measurements of the determinants of glomerular ultrafiltration have greatly expanded our understanding of that process. In addition, these in vivo studies have clarified the dynamics of glomerular ultrafiltration in a number of physiologic and pathophysiologic conditions. Despite this progress, important issues remain unresolved and beyond the scrutiny of in vivo techniques. We have therefore devised a technique for in vitro glomerular perfusion of the isolated dog glomerulus. In eight glomeruli perfused at physiologic rates, the glomerular filtration rate averaged 39 nl/min and the filtration fraction was 0.19. Filtration pressure disequilibrium was observed in all studies and thus allowed calculation of a unique value for the ultrafiltration coefficient. That parameter averaged 2.34 nl/(min X mmHg). Morphologic studies employing transmission electron microscopy indicate that isolated perfused glomeruli remain ultrastructurally intact. The method for glomerular isolation and in vitro perfusion is presented in detail, the results obtained are compared with published in vivo results, and the advantages offered by the technique are discussed.